In ground drilling, in particular in horizontal drilling, an improvement and facilitation of the drilling operation are achieved with the help of drilling fluid and/or mud that are supplied to the drilling device and emerge in the area of the drilling head, for example, and are thereby introduced into the borehole, so that the soil can be softened and the drilling cuttings can be transported away. The cutting action of the drilling head can be improved. In addition, the drilling fluid can serve to lubricate the drilling head and the drill rods driven to rotate when drilling, and consequently, to reduce friction with the ground.
A mixture of water and a mineral, in particular bentonite, and optionally a few additives, which may also be in the form of one or more minerals, is generally used as the drilling fluid or mud. Bentonite is a mixture of various clay minerals with montmorillonite (usually in an amount of 60% to 80%) being provided as the main ingredient. Concomitant minerals may include quartz, mica, feldspar, pyrite and also calcide in some cases. Because of the montmorillonite content, bentonite has a great water absorption and swelling capacity. Water into which a mineral, in particular bentonite, is stirred may have thixotropic behavior. In other words, it may behave essentially like a fluid when in motion but essentially like a solid when at rest. Because of this property, a drilling fluid consisting of water and a mineral, in particular bentonite, may also be used to support the borehole wall, so that a collapse can be prevented.
The drilling fluid is usually prepared in advance and brought to the site of use in large tanks.
DE 199 18 775 B4 describes a continuous mixing system and a method for preparing a drilling fluid, in which a high-pressure pump is provided, having a connection for process water. Furthermore, there is also a connection for a feed medium, which is situated upstream from the high-pressure pump in the direction of flow, so that the feed medium is supplied to the high-pressure pump essentially in an unswollen form. This permits simplified charging of a drilling system with a drilling fluid.
It has been found that there is a demand for producing only as much drilling fluid as needed or to try to use a mixing system and a method as well as a use, which have been optimized for mixing quantities suitable to meet the demand and/or to permit a simplified use, specifically for producing the required amounts and/or facilitate an improvement in the required drilling fluid.